'Reusable' Auto Trans Pan Gasket?

I recently serviced the 4L80E on my 96, it was fine for a month or so - now the trans pan has started leaking. I reused the rubber gasket, as it seemed in good shape. I used my typical procedure (maybe a bad habit), and coated both sides with a thin coat of high temp (red RTV).

Should you not use any RTV with this type of gasket? Or any gasket for that matter?

I got into this habit thinking it might help plug any imperfections of the gasket, especially on a cork-style.

Any secrets to sealing the pan?

Thanks in advance. Joe.

Never use any form of silicone on any transmission.

Best thing is to be certain that teh gasket is absolutely clean and give a good visual inspection for defects prior to reuse.

I've never used any sealant on a transmission pan gasket, and furthermore, always found the orginal reusable pan gasket to be far better quality than the replacements. Mine has a thick rubber seal with wire or steel core. I clean it & reuse.

You'll have to look up the bolt torque values, but I've found under or over tightening to be the cause of many leaks and warped mating surfaces.

Now might be a good time to get the Mag-HyTec pan, which uses an O-ring, and has a (I'm NOT making this up!) REAL DRAIN PLUG! Its baffling and fins along with its aluminum construction really make a difference in cooling.

Shoving my 8T motorhome (with about 100 sq. ft. of frontal area) loads a tranny, and the M-HT pan has lowered temps underway by 20°F. This is substantiated by the fact the temp when creeping in a long highway backup runs around 160°F. When traffic speeds up, it goes back down to the usual 140-145°F. Part of that is due to the pump circulating more, but it's much less than the engine temp; the cooler is in the (very large) radiator.

I did torque the pan to the recommended values - 18 ft-lbs.

Would love the Mag-Hytec pan, but can't really justify the $$ since I don't use this truck for towing.

I'll clean the original gasket/pan real well and give it another shot.

Thanks again for the info. Joe.

If the pan is the stock steel one, be sure that the area around the bolt holes have not been pulled up to the inside edge due to over torqueing.

If the contact area is not nice and flat (except for the little ridges that some pans have, use a piece of steel as an anvil and a small ball peen hammer to tap the rail back flat again.

Use a composit cork/neoprene gasket. The all neoprene ones suck.

Install the gasket dry without any goop of any kind. Tighten the bolts down snug with a short wrench or to MFG recommended torque.

The pans on the 4L80 are not as durable as the ones they uses to use on the TH 400.

Good luck

Missy

It's my understanding that when the 4L80-E left the factory, it came with a re-usable pan gasket. This gasket is a thin aluminum perimeter piece with a neoprene o-ring seal. It's made to be re-used, and is the very best trans gasket I've seen. A dipweed service shop (not GM) will usually discard the great OE gasket when doing a trans service and then install the crappy fiber/neoprene gasket that comes with most aftermarket service kits.

I wrote about the OE gasket some years ago in a related article, but can't put my fingers on the part number right now.... If someone knows, please post it.

Use part# 8685921 for the 4L80-E Automatic transmission oil pan that incorporates a factory drain plug. This pan is listed as being for a 2WD application, but it also fits a 4X4. Only difference between the 2WD & 4WD pans is reported to be the drain plug.

Jim